In the study, people who took aspirin at least twice a week were 27 percent less likely to develop colon cancer over a 28-year period, compared with those who took aspirin less frequently, or not at all.

However, this reduction in risk applied only to colon cancers that did not have a mutation in a gene called BRAF. Taking aspirin regularly did not reduce the risk of developing colon cancer with a BRAF mutation; about 10 to 15 percent of colon cancers have this mutation.